Late audiovestibular consequences of radical radiotherapy to the parotid.

It has been claimed that the inner ear is generally resistant to the effects of radiotherapy schedules commonly used for treating head and neck cancer. A study was made of 28 patients previously irradiated for parotid pleomorphic adenoma to assess the effect on the audiovestibular apparatus. The dose most commonly used was 50 Gy in 15 daily fractions over 20 days and the median interval between radiotherapy and assessment was 14 years. Of 28 patients 15 had significant hearing deficit on the irradiated side on audiometry and this was predominantly sensorineural in type. In addition seven of these 15 patients had semicircular canal paresis. The reason for this morbidity may be arithmetic (total biological dose; dose per fraction) or geometric (upper extent; depth of target volume). Patients are now routinely warned of the possibility of late audiovestibular effects following radical radiotherapy to the parotid.